Manufacturing In order for your sign to be a true asset to your business, you need to be assured that it was “built to last” by a professional manufacturer. National Sign prides itself on its fully equipped, in-house, manufacturing facility. All materials can be utilized to manufacture your sign to your specifications. Another important factor in choosing a sign manufacturer is to assure that they are UL listed for manufacturing electrical sign components. National Sign is one of the few sign manufacturers that are UL listed as well as offering a solid warranty package.